[单项选择]

嘌呤核苷的糖苷键是（）
 

A. Cl＇-N＇糖苷键
B. Cl＇-N₉糖苷键
C. 3＇，5＇-磷酸二酯键
D. 二硫键
E. 肽键

本文以                                比照，主要从                                和知识两个方面对常识教育加以辨析阐释。（4分）

                                                                                Solar Storm
At the end of October 2003, a sudden solar storm hit the earth. A solar storm refers to the large amounts of charged particles released into space (1) the solar energy increases. The release of the energy (2) place along with the activity of the sunspots with a cycle of 11 years. This time, the (3) of the storm exceeded expectations.
This (4) of intense solar storm was caused by the eruption of a solar flare (闪光) and the ejection (喷发)
A. recommends
B. means
C. proposes
D. advises